Production of lignite briquettes



Patented Feb. 2, 1943 PRODUCTION OF LIGNITE BRIQUETTES I Ernest T. Lance and William L. Wells,

Mount Pleasant, Tex.

No Drawing.

Application May 23, 1940,

Serial No. 336,886

2 Claims.

Our invention relates to the making of coal briquettes from finely divided lignite coal and one of the objects of the invention is to provide an economical and practical process for briquettinglignite coal by the use of an adhesive binder such as petroleum asphalt, natural asphalt, coal tar and the like.

The common process of manufacturing coal briquettes is to first reduce the water content of the coal to little more than a trace and then to mix the coal with hot asphalt and/or hot petro leum residual, prior to briquetting. Lignite unlike anthracite and bituminous coal contains from 3035 percent of Water and is highly porous. The water in lignite is present throughout the pores and not as a film on the outside of the coal as is the case with anthracite and bituminous coal. Lignite in natural lump form cannot withstand weathering without breaking up into small lumps or slacking, so that large deposits located in areas where fuel is badly needed are not being developed. A further object therefore is to make available for use, lignite coal by providing a process that will give the coal, weather resistance and' at the same time add tothe available heat units.

Processes now in use for the briquetting of bituminous and anthracite coal are not suitable for the briquetting of lignite at low cost. Hot mixing of asphalt or coal tar with lignite cannot be done practically because lignite contains so much moisture that it cannot be coated with a film in this manner until it is dehydrated almost to completion. n the other hand, if hot asphalt or coal tar is mixed with such dehydrated lignite, the pores of the coal particle will absorb so much of'the asphalt that almost 15 percent asphalt or coal tar will be required before a satisfactory cementing film is produced.

The ordinary method of employing emulsified asphalt, with water in the continuous phase, is not suitable for lignite because emulsified asphalt when used in quantities sufficient to produce a cementing film only adds to the total water content of the lignite which when compressed into briquettes will produce a soft,spongy briquette that will not set up because the water goes into the coal pores and cannot be dehydrated by the ordinary method.

In our process, we heat finely pulverized lignite coal to a temperature from 300-400 degrees 1?. in a-mixing apparatus provided with hot air blowers in order to dehydrate the coal. By this method, the water content is reduced to approximately 10 percent. At theabove specified temperature, the remaining water in the coal is in a heated condition or exists as water vapor and thus keeps the capillaries or pores filled so that it is now -35 percent of the weight of the lignite coal.

The mixture is now dehydrated as before by heating in the mixer and heated air blowing. The water added by the emulsified asphalt is easily evaporated because the pores of the coal are already full of hot expanded water vapor.

Our process results in producing on the coal particles 9. film of asphalt that acts as a primer or sealing agent for the pores, although it does have adhesive properties. Only enough emulsion is used to provide a very thin film on the coal particles. Heated asphalt or coal-tar is now added to, the mixer in an amountfrom about 3-6 percent and the mixing is continued until a uniform thickness of cementing film is produced in the entire mass. The material is now ready for briquetting.

Any mixing equipment that will give intimate contact when the coal and emulsified asphalt are brought together is suitable. Any crushing, grinding and pulverizing equipment that will reduce the coal to the desired size is suitable. The bituminous emulsions we refer to consists of minute particles of asphalt suspended in the aqueous phase and is substantially the same type as is well known in soil stabilization and road building.

We claim:

1. The process for preparing lignite coal for briquetting comprising heating the powdered porous coal to remove a substantial portion but not all of the water from the pores leaving approximately 10 percent and while the coal is in a heated condition with water vapor in the pores, adding thereto, emulsified asphalt with water in the continuous phase to coat the particles and seal the pores and heating the niixture to remove the water from the asphalt and leave a film of the pores, leaving the remaining portion approximately 10 percent in the form of a heated fluid so that the pores of the coal are filled therewith,

priming with emulsified asphalt with water in the continuous phase in the amount of 3-5 percent asphaltic residue of the weight of the lignite coal and when the aqueous phase of the emulsion is dehydrated adding to the mixture 3-6 percent of petroleum asphalt or coal tar.

ERNEST '1'. Lance. WILLIAM L, wnus, 

